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 Re: FM Review: Voigtlander 50mm f/2 APO-LANTHAR | |
Steve Spencer wrote:
DaveFP wrote:
lunar module wrote:
Gads. With all due respect, I really don't understand why so much attention is being paid to the presence of a limited amount of LoCA in this lens, especially considering all of its other superb qualities. Seems like a bit of perseveration is going on here.
There is zero question that it has some LoCA. I think my fountain shots in bright direct backlit sunlight proves this beyond a shadow of a doubt. So does the shot of the waterfall. These findings are unambiguous. The other fountain shots don't really show any LoCA because the lighting is flat and there is no backlighting. But this is helpful too, because it shows that to generate visible LoCA the conditions have to be fairly extreme. And even in extreme conditions the degree of LoCA is limited. The shots that show a bit of LoCA on small tree branches are real, but the severity of the finding is minimal and, IMHO, irrelevant. You have to go looking for it at 1:1 or larger to see it.
I don't own any of the other APO Lanthar lenses so I don't know how the 50 APO compares to the 65 or 110, but I can say that it is vastly better than most of my other non APO lenses. Heck, I see pretty obvious LoCA on my Sony Zeiss 35 1.4 with minimal provocation.
But I would argue that all of this is more or less irrelevant. If you want a lens that has zero LoCA, this isn't it. If you want a lens that has extremely low levels of LoCA which is only visible in extreme conditions and is more or less stellar in every other respect, you owe it to yourself to check this lens out. It is quite special. Don't let the fixation on LoCA in this thread frighten you away.
This lens is small, light, a joy to shoot with and makes beautiful, crispy sharp yet remarkably subtle images. I can more or less guarantee that you will be impressed.
It looks like a wonderful lens but:
There is a history of APO lenses not being particularly APO so if you label a product as such you can be sure that folks are going to test your claim.
If lenses were marketed as "RAPO" (Relatively APO) there would be less discussion.
Part of the problem is that people don't understand what APO actually means. People think it means total absence of CA, which just isn't what APO means. A lens can technically meet the definition of APO and still show CA in some situations. It is true, however, that manufacturers in the past have labelled lenses as APO that do not meet the technical definition. What we should keep in mind is that testing for CA is not the same as testing for whether as lens is APO. It would take some pretty technical testing to actually test for whether a lens is APO, and taking shots of a water fountain or a ruler certainly is not that. Still the test for CA are probably more important for really using the lens, so I think those are the important ones to do. We just shouldn't expect that an APO lens is going to show absolutely no CA, and when a lens does show CA we shouldn't say, "Wo, that lens isn't really APO." It might not be but that test doesn't tell us that. We should expect an APO lens to have less CA, but the amount of CA is important for us to know and we shouldn't expect zero.
I agree with your statement.
And why do people think APO = no CA? Because most review sites suggest that, plus manufacturers seem to claim it, too.
From the Cosina homepage:
"Inheriting the apochromatic optical design, the lens is highly corrected to eliminate optical aberrations including longitudinal chromatic aberration."
They talk about elimination (= absence of CA), which is just nonsense and poor marketing.
http://www.cosina.co.jp/seihin/voigtlander/english/e-e-mount/e-50mmf2.html
[edit] On the German Voigtlander site, the claim is much more relaxed and accurate:
"Durch die apochromatische Korrektur (die Korrektur auf drei, nicht nur zwei Farben), symbolisiert durch die drei farbigen Schrägstriche auf dem Objektiv, werden chromatische Aberrationen nahezu vollständig vermieden."
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